The present invention broadly relates to data systems wherein information is stored on a recording medium, such as magnetic tape and the like. More particularly, however, the present invention is directed to a media carousel changer which can automatically and selectively mount cassettes containing the recording medium and data onto a recorder/reader. This invention specifically concerns a media carousel changer that makes available a plurality of data containing cassettes which can rapidly and efficiently be input into a computer system. The invention also includes automated processes for mounting, reading and demounting media cassettes.
The advent of the information age has seen an exponential growth in the accumulation and storage of data both for on-line usage as well as for archival purposes. In the early days of the computer, before the advent of magnetic disk and optical storage assemblies, data was typically stored on magnetic tapes, such as reel-to-reel tapes and later, cassette tapes. In a magnetic tape storage device, a magnetic coil is used as a transducer to imprint data magnetically on a moving band of magnetic film; thereafter, when the film is advanced across the transducer, the data may be read and re-input into the processor.
Magnetic tape systems have the advantage in that they are relatively low cost. Moreover, magnetic tape can be erased and rewritten many times Nonetheless, other tape storage media have been developed or are possible. For example, optical tapes and laser tapes may be employed in an effort to increase the density of data stored on the medium.
Nonetheless, because of the low cost, magnetic tape is still a highly desirable format for archiving data where the ability to rapidly access the data is less significant and where capital cost is of concern. Once a magnetic tape has been loaded onto a recorder/reader, the accessibility of the data on the magnetic tape is a function of two variables, the density of storage and the speed at which the tape medium may be transported across and accurately read by the transducer. In the overall archiving of data, though, the speed at which the magnetic tape is physically mounted onto and de-mounted from the recorder/reader has great significance. Since manual loading of the tape onto the recorder/reader can be very time consuming, there has been a need for automated library systems for magnetic tapes, either in the form of reels or cassettes.
There are certain difficulties, however, that confront efforts to automate a library of data storage media. On one hand, it is necessary that the cassette or reel be accurately docked by registering and mounting it into the recorder/reader unit. Otherwise, the data on the magnetic tape may not be read, on one hand or, on the other hand, costly damage to the tape media or to the recorder/reader unit may occur.
Once docked, it is necessary that the recording medium be properly threaded through the recorder/reader and, upon completion of the processing, that the recording medium be properly restored into the cassette or onto the tape reel. After completion of this task, it is still necessary to efficiently demount the reel or cassette from the recorder/reader. This sometimes poses difficulties since many recorder/readers include magnetic retainers that help seat a ferromagnetic plate of the cassette or reel for proper mounting. It has proved difficult in the past for automated systems to mechanically break this magnetic coupling when demounting the storage media.
Existing automated systems employ an elevator assembly to mount and demount a cassette into the docking station of a reader. A cassette is advanced in a first translational direction into a region immediately above the docking station but below the threading arm. The elevator assembly then lowers the cassette in a second translational direction into the docking station and the magnetic retainers. As this occurs, the leader block of the cassette is lowered onto and engages an enlargement on the end of the threading arm. To demount the cassette, this procedure is reversed. However, since the elevator assembly raises the cassette in a direction orthogonal to the docking station, substantial force rust be used to break the magnetic coupling between the magnetic retainers of the docking station and the ferromagnetic plates on the cassette.
Accordingly, there remains a need for automated library systems which can access a plurality of modules which store a recording medium so as to mount and demount those modules into a recorder/reader. Such systems need to be capable of accurately docking the recording medium module with the docking station of a recorder/reader and to properly mount the module therein. Such systems must also be able to efficiently demount the module from the recorder/reader and return it to a stored position.
It is an object of the present invention to provide a new and useful media carousel changer which is adapted to receive a plurality of modules which contain a recording medium so as to mount and demount those modules into the docking station of a recorder/reader.
Another object of the present invention concerns a method for automated mounting, reading and demounting such modules or xe2x80x9ccassettesxe2x80x9d.
It is a further object of the present invention to provide a relatively compact data library system in the form of a carousel that can receive a large quantity of stored data that can be easily accessed by a computer processing system.
Another object of the present invention is to provide a carousel changer for recording media wherein modules containing data may be removed from the storage system while another module is being accessed by the recorder/reader.
Yet another object of the present invention is to provide a carousel library system for recording media that is relatively cost effective while at the same time being reliable and efficient.
In order to accomplish these objects, then, a data retrieval system has a carousel changer adapted to receive modules for a recording medium with this carousel changer being operative to mount and demount those modules into the docking station of a recorder/reader. Here, for sake of description, such modules will be referred to as xe2x80x9ccassettesxe2x80x9d which is intended to cover any type of module which receives a recording medium for transport and storage.
The media carousel changer according to the present invention, then, broadly includes a support frame on which a turntable is disposed. The turntable is journaled for rotation about a turntable axis, and a plurality of cassette holders are disposed about a periphery of the turntable. Each cassette holder is adapted to receive a respective cassette containing the recording medium. Each cassette holder is further pivotally mounted to the turntable such that each cassette holder is selectively pivotable between an extended position to move its cassette into a docked state and a retracted position to move the cassette into a stored state.
A rotary drive operates to rotate the turntable to consecutively move each of the holders into registration with the docking station of the recorder/reader. An actuator is provided with this actuator movable between a first advanced position and a withdrawn position. When the actuator is advanced into the first advanced position, it operates to pivot a registered one of the cassette holders into the extended position thereby to move the cassette received therein into the docking station and to dock it with the recorder/reader. When the actuator is moved to the withdrawn position, it permits the registered cassette holder to pivot into the retracted position thereby to demount the cassette received therein from the recorder/reader and withdraw it from the docking station to the stored state.
Preferably, the cassette holders each include a catch operative to engage the actuator as it retracts so that the actuator physically moves the registered cassette holder from the docked relation and out of the docking station. Each of the cassette holders may also include a spring element that is operative to bias the cassette holder into the stored state. Preferably, the actuator includes a plunger arm that is operative to reciprocate between the first advanced position and the withdrawn position and a driver operative to selectively reciprocate the plunger arm. A roller is rotatably disposed on a free end of the plunger arm with the roller assembly operative to engage the registered one of the cassette holders. Here, each of the cassette holders may include a ramp structure with the roller assembly attacking the ramp structure when the plunger arm moves towards the extended state. Contact of the roller assembly with the ramp structure therefore is operative to positively urge the registered one of the cassette holders into the docking station. Upon withdrawal, the roller assembly engages a flange on the cassette holder so that mechanical force is supplied by the actuator with this force tending to demount the cassette.
Each of the cassette holders may also include a resilient latch member which is positioned to retain a respective cassette therein. The cassettes have a leader block which is secured to the recording medium thereof and a detent structure which releaseably holds the leader member in a fastened state with respect to the cassette. Here, the latch member is also sized and positioned not only to retain the cassette in the cassette holder but also to bias the leader member into the fastened state.
The invention also includes the methods implemented by the above described apparatus. The method includes the step of placing cassettes in individual cassette holders and advancing the cassette holders past the docking station of a recorder/reader so that they sequentially come into registration therewith. A selected registered cassette holder and cassette is pivoted, preferably through a 90xc2x0 arc, into the docking station, and the cassette is read. Thereafter, the cassette holder and cassette is pivoted out of the docking station. The pathway is preferably a closed-loop, such as circular. Another cassette holder that is not registered may be pivoted to an intermediate load/unload position so that a cassette may be replaced, for example, while a registered and docked cassette is being read.
These and other objects of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of the exemplary embodiments when taken together with the accompanying drawings, in which: